A molecular dynamics study was made of the effect, upon defect production, of the overlap of collision cascades. A large number of cascades was simulated, and this provided clear evidence that fewer defects resulted when 2 cascades, which had been produced at different times, overlapped. A means was found for defining the spacing of cascades in order to categorize overlap effects. It was found that, when the 2 cascade energies were very different (such as 400 and 5keV), the defects which were produced by the smaller cascade were effectively lost during complete overlap; regardless of which cascade occurred first. Even when the energies were similar, a substantial loss of defects arose when overlap occurred. Such overlap also changed the distribution of interstitial clusters that resulted from the primary damage process in cascades; with a higher proportion of the defects being found in larger clusters.

F.Gao, D.J.Bacon, A.F.Calder, P.E.J.Flewitt, T.A.Lewis: Journal of Nuclear Materials, 1996, 230[1], 47-56